A century ago, the top three causes of death were infectious diseases. More than half of all people dying in the United States died because of germs. Today, they account for a few percent of deaths at most.

We owe much of that, of course, to antibiotics. The discovery of prontosil, the first synthetic modern antibiotic, earned Gerhard Dogagk the Nobel Prize in 1939. Mass-produced penicillin earned Alexander Fleming, Ernst Boris Chain and Howard Walter Florey one in 1945.

It is hard to overstate how much less of a threat infectious diseases pose to us today. But we take antibiotics for granted. We use them inappropriately and indiscriminately. This has led many to worry that our days of receiving benefits from them are numbered.